Audio filtering, forensic enhancement, and examination - before and after samples
The audio recordings that we receive for digital forensic enhancement usually have multiple layers of recorded sound that need to be sifted through and filtered. For example, during 911 calls, you can commonly hear both the person speaking on the phone AND the actual crime in progress and/or distracting noises in the background. Or, for instance, a department store security surveillance camera will capture a crime, but the audio file contains music that obscures the suspects' voices. Sometimes there is surveillance audio recordings taken in prison of an inmate, but that audio contains a mechanical noise, such as an air conditioner or other electronic buzz or hum obscuring a conversation. Audio noise reduction, filtering, and forensic audio editing with the purpose of audio separation and clarification becomes very important in these situations.
With the Ivory Webb case, there were tremendously difficult and loud background sounds that we needed to forensically filter out -- most notably barking dogs and trucks driving past. Here is one sample of before and after work in dealing with that forensics audio issue. (Turn up your speakers to hear the differences.)